Towards Compact, Robust and Highly Stable Optical Frequency References for Space Applications

Abstract

Future space missions from different fields of applications, like global navigation satellite systems (GNSS), next generations of gravity missions or tests of fundamental physics will rely on optical frequency references. While laboratory setups of various optical frequency reference technologies already demonstrate frequency stabilities orders of magnitude better than current microwave references for space applications, another step must be accomplished for high performance optical references in space. One promising technology for this is Doppler-free spectroscopy of molecular iodine, for which we have already developed several iterations of laboratory setups with frequency instabilities down to the 10−15 level for integration times > 100 s. Based on the experience gained from this laboratory setups, we are now working on an iodine reference that will become the first optical clock in space as part of the COMPASSO mission. It will be delivered to the international space station in 2026 for a mission time of 2 years. In addition to the iodine development, we are currently working on a next iteration of a high-finesse optical cavity designed with emphasis on space compatibility to meet the requirements of the next generation of gravity missions. Both technologies together, the iodine spectroscopy unit and the high-finesse optical cavity, should form a hybrid setup suitable for new GNSS architectures.